1. Field of the Invention
This invention relates in general to sound reproduction equipment. In particular, the invention relates to loudspeakers for mounting on a surface, such as a wall, and using the wall to generate sound.
2. Description of the Related Art
Electrodynamic loudspeakers that mount on a wall and that use the wall to create sound are well known. U.S. Pat. No. 3,728,497, issued to Komatsu on Apr. 17, 1973, discloses a typical design. A voice coil is wound on a sleeve affixed to a disk-shaped member having a thick hub with a hole in the center. The sleeve sits in the annular gap of a cylindrical permanent magnet, also having a hole through its center. Vibration of the voice coil is transmitted to the hub through the disk-shaped member. The device is affixed to the wall by a screw that runs through the holes in the magnet and the hub. The device is relatively complex, with a number of spacers, disks and suspension pieces. Since the voice coil is wound on a sleeve, specialized materials and adhesives must be used to withstand the mechanical and thermal stresses that will arise during operation. Some designs also suffer from poor low frequency performance.
A need remained for a device that is simple in design and construction, and which has a minimum of parts. A structure that is rugged and allows the voice coil to withstand large mechanical and thermal stress was also desired, as was a device having acceptable performance at low frequencies. As always, a less expensive structure that is simple to make and use was also desired.